Termination of transcription, like transcription initiation is a highly regulated process and plays a major role in the control of gene expression. The proposed research is to examine thoroughly the process of termination and its suppression in E. coli by phage lambda N gene product, using a combination of cloning, genetics and biochemical approaches. The structure of the N-recognition element in RNA will be determined, and the possible macromolecular interactions involving this element will be studied. The hypothesis that the E. coli NusB protein modulates transcription termination at specific terminators will be tested by genetic and in vitro experiments. The observation that the altered S10 protein in the E. coli nusE mutant unmasks a normally-silent terminator, will be investigated in detail to provide a complete understanding of the role of nus genes in control of termination. The hypothesis that N protein alters RNA polymerase to form a termination resistant transcription complex will be thoroughly examined. Using a coupled transcription-translation system, the role of Nus factors as well as the proposed involvement of ribosomes int his process will be investigated. N-modified transcription complex will be isolated from this system and appropriately labelled components will be used to study the basis of alteration of the transcription complex by N. These studies will provide fundamental information to further our knowledge of the regulation of gene expression.